Manufacture of artificial filaments and the like



NOV. 26, 1940 DREYFUS 2,222,797

MANUFACTURE OF ARTIFICIAL FILAMENTS AND THE LIKE Filed Dec. 24, 1957 HENRY DREYFUS mvsuTOR Patented Nov. 26, 1940 UNITED ST TES MANUFACTURE OF ARTIFICEALFliLAll IENTS AND THE LIKE y Henry Dreyfus, London, England Application December 24, 1937;; Serial 181,715 In Great Britain January 7, 1937 Y 6 Claims. (Grimm).

This invention relates to improvements in the manufacture of artificial materials, and partic-' ularly to improvements in the manufacture of evaporative medium (hereinafter referred to as additional evaporative medium) at a raised 5 temperature is introduced in the vicinity of the shaping device, the total quantity of evaporative medium flowing through the chamber being such that the solvent concentration of the outgoing evaporative medium is of the order of, or less than, that customary in the production of similar solid filamentary materials.

Thus by the present process hollow filaments and similar materials may be produced from solutions of cellulose acetate in acetone with a flow of air or other evaporative medium such,

esses in which a spinning solution is extruded downwards in a chamber through which a counter-current of evaporative medium is flowing,

since it is of most importance in this connection, but it is to be understood that the processes described are also applicable generally to the manufacture of hollow filamentary materials.

The particular temperature for the additional evaporative medium which yields the best results is interrelated with the other spinning conditions, for example the temperature of the other evaporative medium which may be introduced, e. g. near the bottom of the cell, and the nature of the solvent or solvents present in the spinning solution. ihe other evaporative medium which may be employed is referred to in this specification as the main evaporative medium, but it is to be understood that this doesnot imply that the volume of such medium. is necessarily greater than the volume of the additional evaporative medium. The relation between these two volumes is another of'theiactors which maybe adjusted in order to obtain the best results. The additional evaporative medium may; for example, constitute 4F), or Ioreve'n I the-whole of the total evaporative medium flow 'ing through the cell. The greater the quantity of additional evaporative medium the greater in general is the tendency to-theflforrriation 'of' hollowfilaments.

' ln' general it is found that the temperature 10 of the additional evaporativemedium should be above the boiling point of the solvent present in the spinning solution, or in the case of spinning solutions containingmore than one solvent; I

of the solvent or solvents constituting the bulk' of the solvent medium. Preferably,the te'm perature of the additional evaporative medium" is considerably above the boiling point of the solvent constituent of the spinning solution, e." g. 40'or 60 C. above such' temperature. when a solution of cellulose acetate or other cellulo'se derivative in acetoneor other liquid of similar-volatility is employed, the additional evaporative medium may have 'a temperature of for example C. or 'C..

'When a main evaporativemedium'is employed 7 its emperature should in general'be'lowe'r than that of the additional evaporativemedium, e "g.

it"may beGO, 65' or 75 C. In general the higher' 30 the' temperature oithe additional evaporative medium the lower may be the temperature v of 4 themaiii evaporative medium. "Apparatus which maybe employed in carry"- in'g outthe process of the present invention may, '35 for example, comprise an ordinary spinning cell.- containing a jet and adapted for the production of artificial filaments or similar materials by downward. spinning into a counter-current of evaporative medium, and provided with means 40 for introducing additional evaporative medium in the vicinity of the jet. For example, the ad ditional. evaporative medium may be introduced by meansof slotted rings or tubes, and in addition means may be, and preferably are, pro- 45 vided to constrainv the 'whole or' substantially the whole of the total evaporative medium flowing through the cell to pass in the immediate vicinity of the jet, for example by means of "the devices described in U. S. Patent No. 1,814,468. 50"

By causing the whole, or substantially the whole of the evaporative medium to pass in the vicin ity of the jet the manufacture of hollow fiia-' ments may be effected with the additional evap- I orative medium at a lower temperature than '55 solvents and swelling agents.

"acetate, and ethyl and butyl celluloses.

would otherwise be necessary. The additional evaporative medium may be introduced by pressure, or suction may be employed for this purpose.

The additional evaporative medium may be introduced at the plane of the jet face or on either side of said plane and is preferably directed towards the filaments as they issue from the jet. It may, for example, be introduced at points slightly above the plane of the jet face, for example one inch above, and be directed downwards and inwards so that it strikes the filaments at an angle which is less than a right angle. Again it may be introduced some distance below the jet, e. g. at a distance of 8 to 12 inches.

An apparatus which may be employed in carrying out the process of the present invention is illustrated in the accompanying drawing, wherein Fig. 1 shows a vertical cross-section of the upper portion of a spinning cell, andFig. 2 a horizontal cross-section on the line 22 of Fig. 1. I

Referring to Figs. 1 and 2, the apparatus comprises a spinning cell I containing a filter candle 2 connected with a supply of spinning solution (not shown) and with a jet 3. At a small distance below the jet is positioned a device 4 for introducing hot air into the region of the jet, which comprises a hollow ring perforated with holes on the inner side, and connected with an external source of hot air. In order to cause substantially the whole of the evaporative medium employed to pass in the vicinity of the jet a plate 1 having a central hole is positioned below the jet. The evaporative medium passing through the cell is withdrawn through the pipe 8.

In order to obtain the best results it is desirable that the spinning solution should be heated before it issues from the jet, e. g. to a temperathe'vapours of suitable organic substances, e. g.

of benzene, xylene, isopropyl ether and other non- 'solvents'and acetone, methylene ethylene ether,

dioxane, methyl and ethyl acetates and other The presence of vapours of solvents or swelling agents in the additional evaporative media is applicable particularly when filaments of low denier, e. g. 1 or 2 denier, are to be produced.

Spinning may be eiiected at relatively low speeds, for example 100 to 150 metres per minute, or at considerably higher speeds, for example 250 to 300 metres per minute or more.

The process'of the present invention is particularly applicable to the manufacture of arti ficial filaments and similar materials made of cellulose acetate, but it is also applicable to the manufacture of such materials made of other cellulose derivatives, for example cellulose propionate, cellulose butyrate and cellulose nitro- Acetone is, in general, the best solvent to employ, particularly in the case of cellulose acetate, but other volatile solvents may also be employed, for example dioxane, methylene ethylene ether and mixtures of methylene orethylene dichloride with para-toluene sulphonamide. The solutions may 10 also contain non-solvents, provided that they are not present in such proportion as to cause precipitation of the cellulose derivative before the solution is extruded into the cell. Examples of suitable non-solvents are water, benzene, toluene, xylene and ethyl and isopropyl ethers. Preferably the non-solvent if present is less volatile under the spinning conditions than the solvent portion or bulk of the solvent portion 01' the liquid medium.

The cellulose derivative may be present in the spinning solutions in low concentrations, e. g. 20 to 23% or in higher concentrations, e. g. 25%, 28% or 30% or even more.

The artificial filaments, particularly when made from solutions containing high boiling solvents or plasticisers may be drawn down to low denier, e. g. during their travel through the cell or. after issuing from the cell and before being wound.

The following examples illustrate the invention, but are not to be regarded as limiting it in any way:

' Example 1 A 26% solution of cellulose acetate in acetone is extruded vertically downwards through a spinning jet positioned in a spinning cell into a counter-current of air, the temperature of the spinning solution in the jet being about 75 C. About 40% of the total air passing through the cell constitutes the main evaporative medium which is introduced near the bottom of the cell in the ordinary way and which is at a temperature of about 75 C., while the remainder of the total air is introduced in the vicinity of the jet through a slotted ring device which surrounds the bundle of filaments, the slots being so arranged that the additional air, which is at a temperature of about 100 C., is directed inwards on to the bundle of filaments just after they issue from the jet. The total volume of air passing through the cell is regulated so that the solvent content of the outgoing air is about 1.5% by volume. The cell is provided with means such as is illustrated in Figs. 2 and. 3 of U. S. Patent No. 1,814,468 to constrain the Whole of the evaporative medium flowing through the cell to pass in the immediate vicinity of the filaments. The bundle of filaments which issues from the cell is wound or twisted and wound in any suitable manner, e. g. on a cap spinning device.

Example 2 A 20% solution of cellulose acetate in acetone is spun in a similar manner to that described in the preceding example. In this case, however, the temperature of the spinning solution in the jet is about 65 0., the additional air constitutes about 75% of the total volume of the air employed and is at a temperature of about 150 0., the main air is at a temperature of about 60 C. and the total volume of air is such that the solvent content of the outgoing air is about 1% by volume.

Having described my invention, what I desire to secure by Letters Patent is:

1. Process for the production of hollow artificial filaments, threads and other filamentary materials, which comprises extruding a solution of an organic derivative of cellulose in a volatile solvent medium through a jet into a cell into which a current of evaporative medium flows countercurrent to the direction of the filaments formed by said extruded solution and introducing into the cell, and directed towards said filaments, in the vicinity of the jet, an additional current of evaporative medium at a temperature higher than the boiling point of the solvent constituent of said solution, the total quantity of evaporae tive medium flowing through the cell being such that the solvent concentration of the outgoing evaporative medium is from 1 to 2% by volume and the volume of evaporative medium introduced in the vicinity of the jet being at least 40% of that of the total evaporative medium passing through the cell.

2. Process for the production of hollow artificial filaments, threads and other filamentary materials, which comprises extruding a solution of cellulose acetate in acetone downwards through a jet into a cell in which a current of evaporative medium which is introduced near the bottom flows in a direction opposite to that of the .travel of the materials, introducing further evaporative medium at a temperature higher than the boiling point of the solvent constituent of the spinning solution into the cell in the vicinity of the jet, and directing said additional evaporative medium towards the filaments, the total quantity of evaporative medium flowing through the cell being such .that the solvent concentration of the outgoing evaporative medium is from 1 to 2% by volume and the volume of evaporative medium introduced in the vicinity of the jet being at least 40% of that of the total evaporative medium passing through the cell.

3. Process for the production of hollow artificial filaments, threads and other filamentary materials, which comprises extruding a solution of an organic derivative of cellulose in a volatile solvent medium through a jet into a cell into which a current of evaporative medium flows counter-current to the direction of the filaments formed by said extruded solution and introducing into the cell, and directed towards said filaments, in the vicinity of the jet, an additional current of evaporative medium at a temperature of at least C., the total quantity of evaporative medium flowing through the cell being such that the solvent concentration of the outgoing evaporative medium is from 1 to 2% by volume and the volume of evaporative medium introduced in the vicinity of the jet being at least 40% of that of the total evaporative medium passing through the cell.

4. Process for the production of hollow artificial filaments, threads and other filamentary materials, which comprises extruding a solution of cellulose acetate in acetone downwards through a jet into a cell in which a current of evaporative medium which is introduced near the bottom flows in a direction opposite to that of the travel the cell.

5. Process for the production of hollow artificial filaments, threads and other filamentary materials, which comprises extruding a solution of an organic derivative of cellulose in a volatile solvent medium through a jet into a cell into which a current of evaporative medium flows countercurrent to the direction of the filaments formed by said extruded solution and introducing into the cell, and directed towards said filaments, in the vicinity of the jet, an additional current of evaporative medium at a temperature 40 C. higher than the boiling point of the solvent constituent of said solution, the total quantity of evaporative medium flowing through the cell being such that the solvent concentration of the outgoing evaporative medium is from 1 to. 2% by volume and the volume of evaporative medium introduced in the vicinity of the jet being at least 40% of that of the total evaporative medium passing through the cell.

6. Process for the production of hollow artificial filaments, threads and other filamentary materials, which comprises extruding a solution of cellulose acetate in acetone through a jet into a cell into which a current of evaporative medium flows counter-current to the direction of the filaments formed by said extruded solution and introducing into the cell, and directed to- Wards said filaments, in the vicinity of the jet, an

additional current of evaporative medium at a temperature 60 C. higher than the boiling point of the solvent constituent of said solution, the total quantity of evaporative medium flowing through the cell being such that the solvent concentration of the outgoing evaporative medium is from 1 to- 2% by volume and the volume of evaporative medium introduced in the vicinity of the jet being at least 40% of that of the total evaporative medium passing through the cell.

HENRY DREYFUS. 

